1. Field of the Invention
The present invention relates to an information processing device, an information processing method, and a computer program. More specifically, the present invention relates to an information processing device, an information processing method, and a computer program for performing processing for providing content, which is an object of use control, and processing for recording the content in a recording medium.
2. Description of the Related Art
Recently, a DVD (Digital Versatile Disc), a Blu-ray Disc (registered trademark), and the like are used as recording media for content such as music and movies. These information recording media include a medium to which data is recorded in advance and which does not allow writing of new data (ROM type) and a data-writable medium (R type, RE type, etc.). A user is capable of recording a variety of contents via, for example, a network and an apparatus set in a public place by using the data-writable information recording medium.
However, the copyrights, the distribution rights, and the like of most of contents such as music data and image data are retained by creators or distributors thereof. In the distribution of the contents, it is a general practice to impose a certain restriction on the use of the contents, i.e., license only regular users to use the content to prevent illegal copying and the like.
As one of the methods of restricting the use of content, there is a system that encrypts and distributes content and allows only users and apparatuses having proper rights of the use of the content to decrypt the content. A system that encrypts content to control the use of the content is described in, for example, JP-A-2003-116100.
As a standard concerning content copyright protection techniques for realizing a content use form based on the encryption of content, there is the AACS (Advanced Access Content System). Under the standard of the AACS, content is sectioned as units and encrypted content to which unit keys corresponding to the respective units are applied is recorded in a disk. Unit key files in which the unit keys are stored are recorded in the disk as files in which encrypted unit keys are recorded. An MKB (Media Key Block), which is an encrypted block, is also recorded in the disk.
The MKB is an encryption key block generated on the basis of a key distribution system of a tree structure known as one form of a broadcast encryption system. With the MKB, a media key [Km] can be acquired only by processing (decoding) based on a device key [Kd] stored in an information processing device of a user who has a valid license. The user uses the media key [Km] to decode the encrypted unit keys included in the unit key files and acquire the unit keys and decodes the encrypted content using the unit keys.
The control of the use of content by units is realized by sectioning the content by units and allocating the unit keys, which are the encryption keys different for each of the units, to the content to encrypt the content.
When a medium, for example, a disk, having content stored therein is a ROM type disk that allows only reproduction, additional recording of new content in the disk and editing of the new content are not executed. Therefore, the content and key information recorded in the disk are fixed and do not need to be changed. On the other hand, in a content use form in which a medium of the R type, the RE type, or the like that allows writing of data is used, content recorded in the disk is not fixed and processing such as recording of new additional content and deletion and update of the recorded content is executed. According to the deletion and the update of data, processing for adding and deleting unit keys is also necessary.
As processing for recording new content in a disk, for example, processing for downloading content from a content server and recording the content in a medium of the R type, the RE type, or the like and processing for recording the content in the medium of the R type, the RE type, or the like using a terminal placed in a shop or a public space are conceivable.
When content is recorded in a medium anew and provided to a user as described above, the control of use corresponding to respective contents to be provided is necessary. When the medium is a ROM type disk, it is possible to adopt a fixed use control system corresponding to fixed content recorded in the medium. However, in a system that appropriately records content in a medium in which additional recording is possible such as the medium of the R type or the RE type, it is necessary to add or update use control information, key information, and the like in association with content recorded in the medium anew.